It happened when he stopped at the Welcome Break Services on the M74 at about 1.10 pm.
The 34-year-old victim was approached by another man with an Irish accent who asked him for money. He then followed him to the ATM and forced him to withdraw cash at knifepoint.
The culprit made off in a small white van with another man.
Police have described the first suspect as white, aged 40s to 50s with short grey hair and grey stubble. He was wearing a grey jumper and blue jeans.
The second was also white, about 20 years old with short brown hair and was wearing a black and yellow hooded top.
Officers are investigating and Detective Sergeant Mark McLachlan at Dumfries CID said: “This was obviously a very frightening experience for the 34-year-old man and it is vital that we catch the suspects as they may very well do this to others.
“Anyone who may have witnessed the two men hanging around the service station or may have seen them or captured them on dash cam footage is asked to contact police at Dumfries immediately quoting incident number 1622 of 23 November 2020.
“Alternatively, calls can be made to Crimestoppers on 0800 555 111 where anonymity can be maintained.”
The victim was not injured in the incident and continued on his travels to England after reporting it to police.